The current technique for impelling a body through a fluid medium generally involves the action of a propeller to generate the thrust needed to push the body forward. The rotation and the vibration of the propeller and associate shaft, mountings, drive means, etc. generate noise, and an elaborate structural system is needed to mount and hold the propeller assembly in place.
In the known systems employing propellers, it is necessary to provide fluid resistant bearing means in the areas of the hull through which the propeller shafts extend. As wear occurs between the relatively moving bearing means, fluid such as sea water may be able to enter the bilge and if not replaced or repaired will eventually overtax the bilge pumping system resulting in rather serious consequences.